In hoc signo vinces


"In hoc signo vinces" is a Latin phrase conventionally translated into English as "In this sign thou shalt conquer".
The Latin phrase itself renders, rather loosely, the Greek phrase "ἐν τούτῳ νίκα", transliterated as "en toútōi níka", literally meaning "in this, conquer".

History

was an early Christian author who became an advisor to the first Christian Roman emperor, Constantine I, guiding the Emperor's religious policy as it developed during his reign. His work De Mortibus Persecutorum has an apologetic character, but has been treated as a work of history by Christian writers. Here Lactantius preserves the story of Constantine's vision of the Chi Rho before his conversion to Christianity. The full text is found in only one manuscript, which bears the title, Lucii Caecilii liber ad Donatum Confessorem de Mortibus Persecutorum.
The historian bishop Eusebius of Caesaria states that Constantine was marching with his army, when he looked up to the sun and saw a cross of light above it, and with it the Greek words " ", a phrase often rendered into Latin as in hoc signo .
At first, Constantine did not know the meaning of the apparition, but on the following night, he had a dream in which Christ explained to him that he should use the sign of the cross against his enemies. Eusebius then continues to describe the Labarum, the military standard used by Constantine in his later wars against Licinius, showing the Chi-Rho sign. The accounts by Lactantius and Eusebius, though not entirely consistent, have been connected to the Battle of the Milvian Bridge, having merged into a popular notion of Constantine seeing the Chi-Rho sign on the evening before the battle.
The phrase appears prominently placed as a motto on a ribbon unfurled with a passion cross to its left, beneath a window over the Scala Regia, adjacent to the equestrian statue of Emperor Constantine, in the Vatican. Emperors and other monarchs, having paid respects to the Pope, descended the Scala Regia, and would observe the light shining down through the window, with the motto, reminiscent of Constantine's vision, and be reminded to follow the Cross. They would thence turn right into the atrium of St. Peter's Basilica, ostensibly so inspired Saint George.
The Kingdom of Portugal has used this motto since 1139, according with the legend in Lusíadas.

Cultural references

Military

In hoc signo vinces is the motto of: